1. Field of the Invention
This invention relates to a method of preparing an ankle joint for replacement, and more particularly to an ankle prosthesis and a method of preparing the ankle joint for replacement implementing such ankle prosthesis and an alignment apparatus that enables such replacement to be performed from a medial position on the ankle.
2. Background Information
Ankle prostheses and ankle replacement methods have been implemented for the past few decades producing numerous prostheses and approaches to the treatment of diseased, injured or otherwise compromised ankle joints.
Many types of total ankle prostheses have been developed including a cylindrical-type ankle replacement, the spherical-type ankle replacement, the sliding cylindrical-type ankle replacement, the Buechel-Pappas Total Ankle Replacement System, the Scandinavian Total Ankle Replacement system, or STAR system, Hintegra ankle system, ESKA implant, and the Agility™ Total Ankle System. Generally two broad categories exist in ankle replacement prostheses, fixed-bearing ankle implants having fixed components and mobile-bearing implants having mobile components. The fixed-bearing ankle implants are generally semi-constrained, although some are filly constrained, to have a single articulation capability between a tibial and a talar component with some allowance for rotation. The mobile-bearing implants have minimal constraints due to the articulation permitted by a meniscus positioned between tibial and talar components.
Many ankle prostheses in the United States are the fixed-bearing ankle implant type, such as the Agility™ Total Ankle System, due to its FDA approval status. In these types of semi-constrained fixed bearing devices, the tibial prosthesis component and the talar prosthesis component have a plastic insert slidingly positioned within the tibial component between the two components. In these fixed-bearing ankle implants, the two components generally work directly with each other in various fashions and all require incisions and installation from an anterior position on the ankle, save certain methods published for the ESKA ankle replacement.
Most of the known prostheses further require significant amounts of bone to be resected from the tibia and talus in order to install the traditionally bulky components into the ankle joint. As is well known in the art, the more bone that is removed, or resected, the more likely the failure of the component as the bone typically is its hardest at its outside surface. Thus, many devices fail for reasons of subsidence of the component wherein the significant bone resection and the implanting of a component will cause the component to crush into the cancellous bone over time under pressure.
Another ankle replacement that has been developed is the ESKA implant which differs from the other ankle implants in that it requires incision and installation from a lateral position on the ankle. However, this preparation requires the devascularization of the fibula, release of the syndesmotic ligaments and significant bone resection.
No known prosthesis disclosed is designed, configured and installed from a medial position on the ankle.
Some of the most common problems encountered with prior art ankle prostheses are loosening of the components, instability, loss of bone support, subsidence, inadequate motion and noticeable scaring on the most visible parts of the ankle. Further, and more importantly, ankle replacement is more challenging than other procedures such as hip or knee replacement due to the limited soft tissue envelope that is sparse at the ankle and has minimal flexibility. Thus, ankle replacement is associated with a high complication rate. This complication rate is exacerbated by the dense intersection of tendons and nerves in the anterior (or front) and lateral sides of the ankle.
Accordingly, wound problems are not uncommon due to the present techniques and prostheses known in the art.